Preheat the oven to 350F and line 2 baking sheets with parchment paper or a silicone baking mat.
In a medium bowl, whisk together the flour, baking soda, salt, cinnamon, and nutmeg.
In a large bowl, cream together the butter, brown sugar, and molasses on medium speed until well-combined and fluffy, about 3-4 minutes. Scrape down the sides of the bowl.
Add the egg and vanilla and continue mixing until well-combined, about 2 more minutes.
Add the flour and mix on low speed until just combined. Do not over-mix.
Add the oats and chopped dates and stir to combine.
Using a 1.5 tablespoon cookie scoop, scoop the dough onto prepared baking sheets, leaving about 2 inches of space between them.
Bake in the preheated oven for about 11-12 minutes, rotating the sheets half-way through, until the edges are brown and the center looks set.
Cool cookies on the baking sheet for about 10 minutes before removing them to the cooling rack to cool completely.